Heterologous surface display of proteins on recombinant microorganisms involves the targeting and anchoring of heterologous proteins to the outer surface of host-cells such as yeast, fungi, mammalian and plant cells. Display of heterologous proteins at these cells' surfaces can take many forms, varying from the expression of reactive groups such as antigenic determinants, heterologous enzymes, (single-chain) antibodies, polyhistidyl tags, peptides, and other compounds. Heterologous surface display has been applied as a tool for research in microbiology, molecular biology, vaccinology, and biotechnology.